I've also been thinking about doing a continuous water change method, based on diavolume methodology, concentration and diafiltration technology we use in biotech. While lowering the tank volume isn't a concentration step, I was thinking about doing a continuous removal of tank water and addition of fresh water for a certain length of time, which isn't diafiltration because there is no sermi-permeable membrane, it's more of a continuous dilution, that's it. Does anyone know the formula for calculating a continuous dilution, which approaches 100% over time? Don't know if this would be any more beneficial than a 50% water change, but I could approach a higher percentage without having to drain most the tank. I can do this with an additional hose, perhaps I'll even get my first Python! Ideas? Comments? Formula?